1. Field of the Invention
The present invention relates to an air-fuel ratio controller for an internal combustion engine.
2. Description of Related Art
For example, in the Japanese Patent Publication No. 55-4943 (1980), the outputs of an oxygen content detecting means for detecting the oxygen content of the exhaust gases of an internal combustion engine are compared with a predetermined level, and the deviations are integrated and smoothed, and the air-fuel ratio is controlled by feedback depending on the sum of the integrated value and the smoothed value. This smoothing is intended to absorb the individual variations of injectors or the like and the individual differences of parts caused by deterioration of age, and practically it is intended by determining the mean of the integrated values.
Since the integrated value depends on the outputs of the oxygen content detecting means, when these outputs are not normal, for example, when these outputs do not change largely enough over a specific time, the coefficients of feedback control are not corrected properly, so that the air-fuel ratio for a normal operation of the internal combustion engine cannot be done.